Aging is associated with physiological dysfunction, which increases the risk of chronic disease and disability. Coupled with projected increases in the number of older adults, unprecedented levels of dysfunction and disease are expected without intervention. A key aim of this MERIT award R37 AG013038-19 (2004-14) has been to use translational approaches to establish evidence-based strategies for preserving vascular endothelial function with advancing age. Endothelial dysfunction is linked to motor dysfunction and cognitive impairments with aging, and all are related to reduced bioavailability of nitric oxid (NO) and its oxidation products, nitrite and nitrate. Because nitrite is reduced to bioactive NO in the body, recently we have explored the novel strategy of improving systemic NO bioavailability with oral supplementation of inorganic nitrite. Our preclinical studies show that oral sodium nitrite (drinking water) restores NO-mediated vascular endothelial function in old mice, while ameliorating vascular oxidative stress and inflammation, and improving motor function. Preliminary results from our pilot trial in humans support both the safety and efficacy of oral sodium nitrite supplementation for improving endothelial, motor and cognitive function in healthy, primarily late-middle-aged adults, while inducing changes to the plasma metabolome. For the renewal of this long- standing R01/R37 award, we propose to perform a small clinical trial (randomized, placebo control, double- blind) to establish the physiological benefits of oral supplementation of sodium nitrite (80 mg/d x 3 mo) on endothelial, motor and cognitive function in older adults (60-79 yr) without existing functional impairments, disability or chronic diseases. Novel mechanistic insight will be obtained from endothelial cell analysis of oxidative stress/inflammation, brain structure/neural activation (fMRI) and small molecule analysis of plasma. Hypothesis 1: Oral sodium nitrite supplementation will: A) improve vascular endothelial function by reducing oxidative stress; B) decrease endothelial cell markers of oxidative stress and inflammation; and C) induce protection against vascular endothelial ischemia-reperfusion (I/R) injury in older adults. Hypothesis 2: Oral sodium nitrite will improve performance in several subdomains of motor and cognitive function in older adults. Improvements in motor and cognitive functions will be related, and will be associated with changes in endothelial function and brain structure and/or task-induced neural activation patterns. Hypothesis 3: Sodium nitrite will induce changes in metabolites associated with oxidative stress, inflammation and nitrite/NO pathways in older adults related to improvements in endothelial, motor and cognitive function. Impact. Increasing systemic NO bioavailability via sodium nitrite supplementation is a novel, safe and low-cost strategy for improving multiple domains of function and delaying disability and morbidity with aging in humans.